1. Field of the Invention
This invention relates in general to vehicle safety and in particular to vehicle lifting tools.
2. Description of the Prior Art
The work under a vehicle which is standing on the ground is very unpleasant, difficult and dangerous, because poor accessibility and not enough room for movement of hands and tools, that may cause scratches and wounds on hands.
There are several lifting devices which are supplied with vehicles by the manufacturers. One device is a bumper jack which engages a hole in a bumper. It can lift one corner of a vehicle by movement of a metal rod up and down. It can only be used safely for vehicles that have holes in their bumpers.
There are also small pneumatic jacks on the market available for the vehicle owners. A typical jack has four little wheels. By placing it under a vehicle body and rocking a lever, the jack can lift a corner or even a half of a vehicle.
The jack needs skill and knowledge which part of the vehicle is strong enough to support the heavy weight. All of the manually operated jacks have insufficient lifting height, they occupy room under the vehicle and restrict the movement of a person.
For lifting a vehicle only a portable ramp is used on which a vehicle wheel can be moved and lifted 8 inches above the ground. But this ramp can not be used for changing wheel, which is the most frequent occurence in emergency. It is heavy and bulky and can not be carried in the vehicle.
Another tool which is a pivotable linkage device with a scissor type movement of its links, called scissor jack is shown on U.S. Pat. No. 3,741,524 (Morgan). This jack has a threaded driving rod with an enlarged hexagonal head. The jack is placed under the side of a vehicle with its top member 22 engaging a specially provided notch on the body of the vehicle. By turning the rod with a specially supplied wrench, one corner of the vehicle can be lifted and the wheel changed.
The wrench can make only half turn and must be readjusted every half turn, what is a nuissance.
U.S. Pat. No. 4,055,329 (Hammond) shows a jack for stabilizing a parked vehicle. Four such jacks would be permenently mounted on four corners of a vehicle. Both of above cited scissor jacks obstruct the working space and neither engages the tire.
U. S. Pat. No. 3,252,369 (Gridley) shows a large structure on wheels with a platform for lifting construction material on a building site. Besides that it has links it has no other similarity to the vehicle lifter.
Pat. No. 546,545 (Wagner), Germany and U.S. Pat. No. 1,408,408 (Scott). Both these patents show a stationary, horizontal platform of a large size for a convenient work on motorcycles. The platform can be inclined to the ground and after the motorcycle would be moved on it, the platform would tilt back to horizontal level by gravity force, as it is pivotally supported. Wagner shows also a hydraulic brake for preventing bumps.
U.S. Pat. No. 1,401,463 (Cordes) and U.S. Pat. No. 4,486,006 (Fawdry). Both these references show a very large stationary platform pivotally mounted which can be inclined to the ground level and a four wheel vehicle could be driven on the platform. When the vehicle would pass the pivotal point the platform would tilt by the vehicle weight to horizontal level determined by multiple supports. To prevent damage of the structure by heavy bumps and control the tilt, telescopic dampers are provided. Platform of Cordes is shaped like frame with openings in the center to allow the work on the underside of the vehicle. It differs greatly from the small lifter as to the size, construction and operation.
Fawdry patent shows two separate tracks for a four wheel vehicle. The tracks have separate pivots, supports and dampers. But driving on the narrow and long tracks, which are not rigidly joint may be risky.
U.S. Pat. No. 2,071,470 (Marlowe) shows scissor jack, which has the top member called dishhead bearing plate supported on two pins and is not pivotable. It is adapted to engage the body of a vehicle, preferably the axle. It has two stage of operation. First its dishhead bearing plate is brought in contact with the load by manually turning a crank mounted on the driving rod, then by using horizontally operated ratchet wrench, the driving rod is turned through a gear system to lift the load.